I love the style of this artwork, but I can't help but wish the eyes had a little more detail to them. My favorite is the character on the left, the shading seems a bit better on that character- and it flows a bit more freely. I might change the angle it's right arm is at, as it looks like it's coming out of its mouth. Moving it a little over more towards the collar would fix this. The tail is also bent kind of oddly. Since I'm assuming this is a dog, dogs tails don't generally curve at that much of an angle, so it could be a little confusing to the viewer.
The character to the right has excellently done blush on it's cheeks, and the collar has a bit more contrast, which could've been beneficial to the character on the left. What I didn't really like was the spot on the left ear and the left arm where there's a transparent spot between the actual rest of the body and the appendage. It kind of gives me the feel that part of the dogs body is not attached, which is mildly disturbing.
All in all, I love the simplicity of the style, and I love the innocence that the child-like style has to it. The issues I mentioned are really minor, but I feel if they were fixed it would really make the drawing flow better.
Haha, if you need more practice you should offer like 1$ quickies of those. I'm sure you'd get a bunch of requests, and that would give you the freedom to only do the ones that are simple enough for that style/you like the most. ^.^
Or you could just make up a bunch of characters and auction them off as adoptables.